The sense coil of the vehicle detector is an important part of the parking lot management system, and its working stability directly affects the operating effect of the entire system. Therefore, the production of the geomagnetic coil is an important part of the project installation process. The following points should be noted when making sense coils:
First, the coil material
Under ideal conditions (regardless of the influence of all environmental factors), the detector coils are buried only with regard to the size (or circumference) and number of turns of the area, regardless of the material of the wire. However, in practical engineering, the mechanical strength of the wire and the anti-aging problem at high and low temperatures must be considered. In some harsh environments, the problem of acid and alkali resistance must also be considered.
The detector will not work as soon as the wire is aged or the tensile strength is not enough to cause the wire to break. In practical projects, it is recommended to use a multi-stranded copper core tinned wire (high temperature wire, AF200X FEP) with a standard cross-sectional area of ​​1.0 mm or more.
Second, the coil shape
2.1 Rectangular installation
Usually the search coil should be rectangular. The two long sides are perpendicular to the direction of movement of the metal objects. The distance between them is recommended to be 1 meter. The length of the long side is determined by the width of the road, which is usually 0.3 meters to 1 meter narrower than the distance between the roads.
2.2 Tilted 45° Installation
In some cases when it is necessary to detect a bicycle or a motorcycle, consider installing the coil at an angle of 45° to the direction of travel.
2.3 "8" font installation (not recommended, you must try)
In some cases, when the road surface is wide (more than six meters) and the chassis of the vehicle is too high, this type of installation can be used to disperse the detection points and increase the sensitivity. This type of installation can also be used for sliding door detection, but the coil must be close to the sliding door (about 1 meter).
Third, the number of turns of the coil
In order to operate the detector in the best condition, the inductance of the coil should be maintained between 100uH-300uH. With the coil inductance constant, the number of turns of the coil has an important relationship with the perimeter. The smaller the perimeter, the more loops there are.
Generally refer to the following table:
Since there may be buried under the road with various metal materials such as cable lines, steel bars, and sewer covers, these will have a great influence on the actual inductance of the coil. Therefore, the data in the above table is for reference only. In actual construction, the user should use the inductance tester to actually test the inductance value of the vehicle detector coil to determine the actual number of turns, as long as the final inductance of the coil is within the best working range (eg between 150uH and 300uH). ).
Fourth, the production plan
4.1 Determine the location of the embedment: Determine the location of the coil and the direction of the wire according to the site conditions (pavement width, diversion of people and vehicles, presence or absence of other coils, and whether the ground has high-voltage cables, steel mesh, etc.).
4.2 determine the coil size: according to the ground conditions, whether there are other coils (the number of adjacent coils must be staggered) and the type of vehicles to determine the shape of the coil, length and width, number of turns and other specifications.
4.3 Determine the cured product: Select the cured product according to the ground type and operating conditions. 1, mud plus 107 glue or cement 2, asphalt 3, epoxy resin.
Fifth, laying method
5.1 Grooving:
After completing the coils and leads according to the plan, use the road cutting machine to cut the slot on the road surface, and carry out 45-degree chamfering on the four corners to prevent the sharp corner from damaging the coil cable. Groove width is generally 4 to 8 mm and depth 30 to 50 mm. At the same time, a slit for the coil lead to the curb must be cut.
Note: The cutting groove must be cleaned of free metal shavings and ** sharp sand, water and other liquid infiltration.
5.2 Coiled coils:
The coil must be straightened when it is wound, but do not stretch too tightly and close to the bottom of the groove. Leave enough wire long enough to connect to the vehicle detector and ensure that there is no joint in the middle. After winding the coil, the outgoing cable must be made in a tight twisted pair (requiring 20 twists per meter). The output leads are drawn through the lead slots.
After the winding of the coil is completed, the inductance value of the vehicle detector coil should be actually tested using an inductance tester, and the inductance of the coil should be between 100uH and 300uH. Otherwise, adjust the number of turns of the coil.
Note: The sensitivity of the vehicle detector coil decreases as the length of the lead increases, so the length of the lead cable should be as short as possible (usually should not exceed 5 meters), untwisted output leads must cause crosstalk, and the vehicle detector coil The instability of the inductance value causes the vehicle detector to malfunction.
5.3 Burial:
After the winding of the coil is completed, a nylon rope or a layer of fine sand may be wound around the coil to enhance protection. Finally cut the groove with asphalt, cement or epoxy resin.
Six, matters needing attention
6.1 coil material: standard 1.0 square high temperature tinning line.
6.2 There must not be a large amount of metal within a range of 1 meter around, such as manhole cover, storm drain cover, etc.
6.3 There shall be no more than 220V power supply lines within a range of 1 meter around.
6.4 When multiple coils are used, the distance between the coil and the coil must be greater than 2 meters, otherwise they will interfere with each other.
6.5 The standard 3 meter wide road, vehicle detector coil size is 2 meters long and 1 meter wide, 45 degrees, 10 centimeters long chamfered corners.
As shown below:
6.6 The distance between the coil and the roadside is about 50 centimeters, and the coils are vertically overlapped with 4 to 8 turns, with a total length of 40 to 80 meters (including lead wires).
6.7 buried trunking cutting parameters: width 4mm, depth 50-80mm, depth and width should be uniform, should try to avoid suddenly deep shallow, suddenly wide and narrow situation.
6.8 Coil should be in the same balance position as the barrier or control machine.
6.9 The two wires drawn from the coil should be twisted with a density of no less than 20 knots per meter. Untwisted output leads will cause interference. The output lead length is recommended not to exceed 5 meters. Since the sensitivity of the detection coil decreases as the length of the lead increases, the length of the lead cable must be as short as possible.
6.10 After the well is laid down, apply cement, asphalt, epoxy resin and other materials to seal and solidify the notch. For the above three kinds of materials can be used on the cement pavement, asphalt or epoxy resin can be used for the asphalt stone pavement, the use of asphalt sealing should pay attention to the coil.
6.11 There must be no debris in the cut groove, especially if there is no **. Clean it first.
6.12 The slot of the detector coil of the vehicle should be cut into the area of ​​the safety island to prevent the lead from being exposed on the road surface.
6.13 When winding the coil, you must straighten the coil, but do not stretch too tightly and close to the bottom of the groove. Do not create staggered layers. After winding the coil, the twisted output lead is led out through the lead slot.
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